Transcript Environmental Pollution - II.ppsx

eCourseware@AIKTC
EFFECTS OF AIR POLLUTION : PHOTOCHEMICAL SMOG
Dec ’12, ’13,
Jun ‘13
• Photochemical Smog is the
haze
in
the
atmosphere
accompanied by high levels of
ozone and nitrogen oxides,
caused by the action of sunlight
and pollutants.
• Smog = smoke + fog
• Cities like Los Angeles, New York, Sydney and Vancouver frequently
suffer episodes of photochemical smog.
EFFECTS OF AIR POLLUTION : PHOTOCHEMICAL SMOG
• Causes/Pollutants Involved :
 Nitrogen Oxides
 Volatile Organic Compounds
 Ozone
 Peroxyacetyl Nitrates (PAN)
• Conditions for Photochemical Smog :
 Source of Nitrogen oxides and VOCs
 Time of the day
 Meteorological factors (precipitation, wind, temperature)
 Topography
Dec ’12, ’13,
Jun ‘13
EFFECTS OF AIR POLLUTION : PHOTOCHEMICAL SMOG
• Chemistry of Photochemical Smog :
O3 + NO» NO2 + O2
NO + RO2 » NO2 + other products
NO2 + sunlight » NO + O
O + O2 » O3
NO2 + R» products such as PAN
Dec ’12, ’13,
Jun ‘13
EFFECTS OF AIR POLLUTION : PHOTOCHEMICAL SMOG
Dec ’12, ’13,
Jun ‘13
• Effects of Photochemical Smog :
 Decreased visibility
 Heart and lung problems
 Suppression of plant growth
 Decreased immunity
 Spread of cancer
 Eye irritation
 Respiratory problems
 Bronchial congestion
 Harsh odour
• Remedies :
 Decrease of nitrogen oxide and
VOC emissions
In the AREAS AFFECTED section of the Wikipedia
page for Photochemical Smog, can you guess
which city comes first?
CASE STUDY: LONDON SMOG
• Date: 5th – 9th December, 1952
• Location: London, England
• London Smog or Great Smog
of 1952 or Big Smog was a
severe air pollution event.
• A period of cold weather,
combined
with
an anticyclone and windless
conditions, collected airborne
pollutants (mostly arising from
the use of coal) to form a thick
layer of smog over the city.
• It lasted for 4 days and then
dispersed quickly when the
weather changed.
• It lowered the visibility and
penetrated into indoor areas
causing breathing problems.
CASE STUDY: LONDON SMOG
• 4,000 people
prematurely
had
died
• 100,000 more were made ill
because of the smog's effects on
the human respiratory tract.
• It is known to be the worst airpollution event in the history of
the United Kingdom.
• It led to several changes in
practices
and
regulations,
including the Clean Air Act 1956.
• It was significant in terms of its
effect on environmental research,
government regulation, and public
awareness of the relationship
between air quality and health.
ELECTROSTATIC PRECIPITATOR
An electrostatic precipitator (ESP) is a filtration device that removes
fine particles, like dust and smoke from a flowing gas using the force
of an induced electrostatic charge minimally delaying the flow of
gases through the unit.
ELECTROSTATIC PRECIPITATOR
Row of Thin Vertical Wires
Negative Voltage of
Several Thousand Volts
Stack of Large Vertical
Flat Metal Plates
Air Stream
Flows Horizontally
Schematic Diagram of Electrostatic Precipitator
ELECTROSTATIC PRECIPITATOR: WORKING
• Electrostatic precipitators contain a row of thin vertical wires and
followed by a stack of large vertical flat metal plates, with the plates
typically spaced about 1 cm to 18 cm apart, depending on the
application.
• The air stream flows horizontally through the spaces between the
wires, and then passes through the stack of plates.
• A negative voltage of several thousand volts is applied between
wire and plate.
• If the applied voltage is high enough, an electric corona
discharge ionizes the air around the electrodes, which then ionizes
the particles in the air stream.
• The ionized particles, due to the electrostatic force, are diverted
towards the grounded plates.
• Particles build up on the collection plates and are removed from
the air stream.
VENTURI SCRUBBER
• Venturi scrubbers are a
traditional
&
well-known
method for removing fine dust
particles from industrial air
streams.
• Venturi scrubbers are often
installed to remove fine
particles
from
volatile,
hazardous or corrosive gas
streams or gas streams
containing solid materials that
are difficult to handle.
• They have been widely used
throughout
the
chemical
industry for decades.
Dec ’12,
Jun ‘13
VENTURI SCRUBBER
Schematic Diagram of Venturi Scrubber
Dec ’12,
Jun ‘13
VENTURI SCRUBBER: WORKING
Dec ’12,
Jun ‘13
• A venturi scrubber consists of three sections: a converging section, a
throat section, and a diverging section.
• The inlet gas stream enters the converging section and, as the area
decreases, gas velocity increases (in accordance with the Bernoulli’s
equation).
• Liquid is introduced either at the throat or at the entrance to the
converging section.
• The inlet gas, forced to move at extremely high velocities in the small
throat section, shears the liquid from its walls, producing an enormous
number of very tiny droplets.
• Particle and gas removal occur in the throat section as the inlet gas
stream mixes with the fog of tiny liquid droplets.
• The inlet stream then exits through the diverging section, where it is
forced to slow down.
• Venturis can be used to collect both particulate and gaseous pollutants,
but they are more effective in removing particles than gaseous pollutants.
NUCLEAR POLLUTION
Nuclear pollution is pollution that contains radioactive elements.
Nuclear pollution may be in the air, water or on land.
NUCLEAR POLLUTION: CAUSES
• Nuclear pollution is caused by a range of human activities that
relate to the creation of fuel for nuclear energy and the construction
of nuclear weapons.
• The process of mining and processing uranium ores to create fuel
for nuclear power and weapons also generates by-products that are
radioactive.
• The largest amount of nuclear pollution was generated due to
detonations of nuclear weaponry.
• The weapons were detonated in combat during the end of World
War II and as part of various weapons testing and experimentation
processes.
• The production of nuclear weapons also generates a minimal
amount of radiation due to the radioactive materials used in the
process.
NUCLEAR POLLUTION: CAUSES
• The handling and disposal of nuclear waste generated from nuclear
power plants typically generate low to medium levels of radiation
pollution over time.
• Nuclear waste is generally treated and disposed of in remote areas,
such as abandoned mines or remote caves.
• However, pollution generated by these wastes can spread into the
soil, water and air around the storage location over time as both
natural and artificial shields deteriorate.
• Nuclear accidents, such as those in Chernobyl in 1986 and Three
Mile Island in 1979, can also lead to significant amounts of radiation
pollution being dispersed into the air and the area surrounding a
nuclear plant.
NUCLEAR POLLUTION: EFFECTS
• Direct effect of a nuclear blast is damage to life and property. This
explosion is most serious in places of higher altitude. The blast range
increases with height gain.
• The blast winds are much more powerful than a hurricane.
• A nuclear explosion releases large amounts of radioactive
substance. This can cause damage to the eyes. The retina of the eye
can either become blinded due to the intensity of the infra red rays
or it can melt because of the high temperature release.
• The tremendous heat output will result in burn injuries, both to the
skin and to the skeletal system.
• Gamma rays will cause metal wires to act as antennas and produce
high voltage. This voltage will result in permanent damage of wires.
NUCLEAR POLLUTION: EFFECTS
• Earthquakes can occur as an aftermath to nuclear blasts. The
pressure wave will travel from the underground to the area of
explosion and cause a quake of great intensity.
•It will result in the death of many living organisms. Those that
survive will show symptoms of radioactive poisoning.
• In the survivors, gene mutation will occur as a result of the
radiation. This mutation will bring serious health hazards for the
future generations.
• The explosion will have negative impact on the environment and
the atmosphere.
CASE STUDY: FUKUSHIMA DISASTER
• The
Fukushima
Daiichi
nuclear disaster was a
nuclear energy accident at
the Fukushima I Nuclear
Power Plant in Fukushima,
initiated
primarily
by
the
tsunami
following
the Tōhoku earthquake on 11th
March 2011.
• Immediately
after
the
earthquake,
the
active
reactors automatically shut
down their sustained fission
reactions.
• However,
the
tsunami
destroyed
the
emergency
generators cooling the reactors,
causing reactor 4 to overheat
from the decay heat from
the fuel rods.
CASE STUDY: FUKUSHIMA DISASTER
• The insufficient cooling led to three nuclear meltdowns and
the release of radioactive material beginning on 12 March.
• Several hydrogen-air chemical explosions occurred between 12
March and 15 March.
• The Fukushima disaster is the largest nuclear disaster since the
1986 Chernobyl disaster and the second disaster to be given the
Level 7 event classification of the International Nuclear Event Scale.
• Though there have been no fatalities linked to radiation due to the
accident, the eventual number of cancer deaths caused by the
accident is expected to be around 130-640 people in the years and
decades ahead.
• There are no clear plans for decommissioning the plant, but the
plant management estimate is 30 or 40 years.
• A frozen soil barrier is being constructed to prevent ongoing
exposure of running groundwater with melted-down nuclear fuel.
Thank you!